The expression "you are what you eat" motivates some people to eat better. Little could they have known just how true this may be. A new study shows food may be literally changing us from the inside out. Researchers at Nanjing University in China discovered plant microRNA in the blood and tissue of humans and other plant-eating mammals, something no scientist knew was possible.

Surprisingly, some plant genetic material is not broken down by the digestive fluids nor is it killed by boiling water. Chen-Yu Zhang, a molecular biologist who led the Nanjing study, found plant microRNA not merely roaming the blood of human subjects, but changing cellular function. If true, this suggests food has the potential to alter human cells.

MicroRNAs are inside every cell. They're important in the production of proteins, which do nearly all the work of a cell. They're one of several types of RNA produced from DNA. MicroRNA and another called messenger RNA, or mRNA, both travel outside the cell nucleus to the cytoplasm. Once there, mRNAs, which carry instructions, are translated by ribosomes into proteins, and microRNAs control how quickly that translation happens.

In all, Zhang and his colleagues found 30 plant microRNAs in the blood of humans and cows. Two in particularly high levels are MIR156a and MIR168a, which are also high in rice, brussel sprouts, broccoli, cabbage and cauliflower. Researchers took the study a step further by testing whether these two plant microRNAs are impacting cellular processes.

For microRNAs to influence the production of proteins, they have to bind to mRNAs. Zhang's team found that MIR168a had the ability to bind to 50 mammalian mRNAs, in particular one in the liver. In studies with mice, MIR168a bound with a mouse mRNA in the liver to slow its production of a protein that helps remove low density lipoprotein, known as the "bad" cholesterol, from the blood. Could this be the "revenge of the plants"?

The researchers hypothesize that once the plant microRNA is eaten, it's absorbed by cells lining the stomach wall, then it enters the bloodstream and travels to various organs such as the liver. Since microRNAs are found in every cell scientists have examined, everything people eat could be influencing a myriad of mRNAs inside the body, thereby affecting how cells function.

It's possible mammalian diets have been influencing physiology and evolution from the beginning. This is not the first evidence of food altering the eater. The green sea slug Elysiachlorotica steals genes for photosynthesis from its favorite snack, green algae. Also, mice fed soybeans have been shown to take up plant's genetic information. If the Nanjing study can be verified, it could open a whole new field of research on how diet impacts disease.

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Plant RNAs Found in Mammals
A very readable description from New Scientist of this surprising research that demonstrated that microRNAs from plants accumulate in mammalian blood and tissues where they can influence the utilization of genetic information.